The present invention relates to prepared foods, such as fried snack foods, fortified with non-esterified phytosterols delivered in fats or oils that are essentially free of emulsifiers and the like, and to the utility of such phytosterols for stabilizing heated fats and oils against oxidation, as well as to the surprising bioavailability of triglyceride-recrystallized phytosterols in such foods, for decreasing plasma cholesterol levels in mammals.
It has been a widely held belief that to obtain appreciable benefit from phytosterols, i.e., either plant sterols, stanols, or combinations thereof [including beta-sitosterol, beta-sitostanol, campesterol, campestanol, stigmasterol, stigmastanol, brassicasterol, brassicastanol, clionasterol and clionastanol (collectively termed phytosterol or phytosterols)] for lowering plasma cholesterol, the phytosterol should be dissolved in an edible oil or other solvent so that it can enter micelles in the small intestine to inhibit the absorption of cholesterol.
This belief has been supported by early research carried out in the 1950s through the 1970s showing that large doses of phytosterols in their solid form, i.e., coarse powders, were required to achieve meaningful decreases in plasma cholesterol levels. For example, in 1956, Faquhar et al., (Circulation, 14, 77-82, 1956) showed that doses of 12-18 g per day of beta sitosterol (provided in divided doses) were required to achieve a 15-20% lowering of serum cholesterol in males with atherosclerosis. In another study, 9 g per day (3 g t.i.d.) of soybean-derived phytosterols were required to lower plasma cholesterol approximately 9% (Kucchodkar et al., Atherosclerosis, 23, 239-248, 1976). In yet another study, 3-9 g per day of tall oil-derived phytosterols were required to lower plasma cholesterol approximately 12% (Lees et al., Atherosclerosis, 28: 325-333, 1977). In a recent study, 1.7 g per day of finely powdered tall oil-derived phytosterols were sufficient to lower total plasma cholesterol by 9% and LDL-cholesterol by about 15% (Jones et al., Am J Clin Nutr, 69: 1144-1150, 1999).
It has been generally appreciated that phytosterols such as alpha and beta sitosterol, stigmosterol, campesterol, and the corresponding saturated (chemically reduced or hydrogenated) xe2x80x9cstanolxe2x80x9d species, are insoluble in water, and only slightly soluble in edible oils. Accordingly, to promote the solubilization of phytosterols, and their efficacy in lowering plasma cholesterol, U.S. Pat. No. 6,025,348 by Goto et al. describes the incorporation of at least 15% and as much as 70% by weight or more of a polyhydric alcohol/fatty acid ester (including glycerol fatty acid esters containing at least two esterified and at least one unesterified hydroxyl group such as diacylglycerols or diglycerides), into a fat. Between 1.2% and 4.7% by weight of phytosterol is incorporated into the polyhydric alcohol/fatty acid ester containing fat composition.
U.S. Pat. No. 6,139,897 by Goto et al. describes an oil or fat composition containing 80% or more diacylglycerol and up to 20% phytosterol. The high proportion of diacylglycerol assures solubility or dispersal of the phytosterol to provide a cholesterol-lowering fat substitute.
U.S. Pat. No. 5,998,396 by Nakano et al., describes an edible oil containing a phytosterol, vitamin E, and an emulsifier rendering the phytosterol soluble in both the vitamin E and the edible oil.
U.S. Pat. No. 5,419,925 by Seiden et al. describes a reduced calorie fat composition based upon a substantially non-digestible polyol fatty acid polyester plus reduced calorie medium chain triglycerides and other reduced calorie fats or noncaloric fat replacements including plant sterol esters that are soluble in such fat compositions. Free fatty acids, vitamin E and tocotrienol have each been utilized by other inventors to promote the solubilization of phytosterols in fats and oils, with the expectation that the cholesterol lowering properties of various phytosterols would be improved.
U.S. Pat. No. 5,244,887 by Straub describes the preparation of a cholesterol-lowering food additive composition with plant stanols, including: (i) an edible carrier such as an oil, monoglyceride, diglyceride, triglyceride, tocopherol, alcohol or polyol, (ii) an antioxidant and (iii) a dispersant or detergent-like material such as lecithin, or other phospholipids, sodium lauryl sulfate, a fatty acid, salts of fatty acids, or a fatty acid ester. Straub cites research showing that 1.5 grams per day of a stanol mixture derived from soybean sterols lowered blood cholesterol by 15% after 4 weeks of therapy, and believes that these stanols are preferred to sterols based upon less stanol absorption from the G.I. tract and better heat stability in air than sterols.
U.S. Pat. No. 5,932,562 by Ostlund, Jr. describes an aqueous micellar mixture of plant sterol and lecithin (in a 1:1 to 1:10 mole ratio) which has been dried to a water soluble powder and which is useful as a food additive for reducing cholesterol absorption.
U.S. Pat. No. 4,195,084 by Ong describes a taste-stabilized pharmaceutical suspension of sitosterols to reduce hypercholesterolemia, in which the suspension includes the plant sterol, a chelator such as calcium disodium EDTA, a surfactant and other ingredients to assure suspension and dispersal of the phytosterol.
U.S. Pat. No. 3,881,005 by Thakkar et al. describes a pharmaceutical dispersible powder for oral administration in which sitosterols are combined with any one of a variety of excipients, and any one of a variety of pharmaceutically acceptable surfactants.
U.S. Pat. No. 6,267,963 by Akashe et al. describes a plant sterol/emulsifier complex that has a lower melting temperature than the plant sterol alone. The complex, e.g., a co-crystallized monoglyceride and plant sterol mixture, is said to facilitate incorporation of the sterol into food products without adversely affecting the texture of the food products.
As indicated above, it has been widely believed that increasing the solubility of phytosterols in fat increases their bioavailability and reduces the dose required to achieve a specified degree of cholesterol reduction. Thus, U.S. Pat. No. 5,502,045 by Miettinen et al., describes the preparation and use of the plant stanol, beta sitostanol, in the form of a fatty acid ester which is readily soluble in an edible oil, to reduce the serum cholesterol level in humans. This technology has been utilized in manufacturing the margarine product marketed under the tradename Benecol(copyright).
U.S. Pat. Nos. 6,031,118 and 6,106,886 by van Amerongen et al. describe similar stanol fatty acid esters but provide different and reportedly improved chemical methods for their preparation. Plant sterols(from soybean oil) have also been interesterified with fatty acid esters to produce the margarine marketed under the tradename Take Control(copyright). Clinical studies suggest that with mildly hypercholesterolemic individuals, dietary intake of between 1.5 and 3 grams per day of the free phytosterol (provided in a fatty acid esterified form) is required to decrease plasma cholesterol approximately 15%.
U.S. Pat. No.5,932,562 by Ostlund, Jr. points out that cholesterol is absorbed from an intestinal micellar phase containing bile salts and phospholipids which is in equilibrium with an oil phase inside the intestine. Prior to recent experiments, delivery of phytosterol as a solid powder or aqueous suspension was thought to not be preferred because of the limited rate and extent of solubility in intestinal liquid phases. In fact, at least two earlier human studies showed that as much as 9-18 grams of sitosterol per day were required to decrease the plasma cholesterol level by approximately 15% when the sitosterol was provided in a coarse powdered (rather than soluble) form. Yet, esterification of phytosterols, coupled with the use of edible oils to deliver these sterols is not always practical, e.g., in formulating fat-free foods. It is in this context that Ostlund, Jr. provides a water-dispersible mixture of plant sterol and lecithin.
Using a finely milled powdered form of free phytosterols (from tall oil) suspended in a margarine (not fully dissolved or recrystallized in fat), Jones et al. have described cholesterol reduction in hypercholesterolemic humans (Jones et al., Am J Clin Nutr 69: 1144-1150, 1999) and other mammals (Ntanios et al., Atherosclerosis, 138: 101-110, 1998; Ntanios et al., Biochim Biophys Acta, 1390: 237-244, 1998). In these studies, the efficacy based on cholesterol reduction appears to be equal to that of phytosterol and stanol esters reported by others.
Still another method of producing a fine suspension of microparticulate phytosterols in fat and water has been described by Yliruusi et al. in PCT International Publication Number WO 99/43218. The method involves first heating and dissolving beta-sitosterol in a fat or oil, and then precipitating the phytosterol with water to form a homogenous microcrystalline suspension. While this process appears more cost-effective than grinding, emulsification of fat with water causes any fat to become susceptible to oxidation and necessitates refrigeration.
The production of microparticulate phytosterols described in the prior art involves increased cost and inconvenience, e.g., the use of grinding, and can result in a mixed emulsified product that is more susceptible to oxidation and rancidity, particularly when an aqueous fat-phytosterol emulsion is involved. In fact, there are limitations and disadvantages inherent in most of the above prior methods of phytosterol preparation and delivery. These methods have included grinding, formation of fat and water mixed phytosterol emulsions, chemical modification of phytosterols, e.g., esterification, and mixing of phytosterols with substantial amounts of specialized solubilizing and dispersing agents.
A recent review article entitled xe2x80x9cTherapeutic potential of plant sterols and stanolsxe2x80x9d (Plat et al., Current Opinion in Lipidology, 11: 571-576, 2000) has summarized the results of a number of independent clinical studies in which human plasma cholesterol levels were monitored before and after ingestion of food products enriched with plant sterols and sterol esters (approximately 2-2.5 g per day). The authors conclude that LDL cholesterol levels decreased significantly, i.e., an average of 10-14%.
The description above is provided to assist the understanding of the reader, and does not constitute an admission that the cited references are prior art to the present invention.
The present invention concerns the use of non-esterified phytosterols in fortifying fat-containing prepared foods. Non-esterified phytosterols were found to have the unexpected property of decreasing the oxidation of fats used in prepared foods, particularly when the fats are heated and become particularly susceptible to oxidation. It is believed that soluble phytosterols e.g., the heat-solubilized non-esterified phytosterols described herein, are also able to protect polyunsaturated fatty acid moieties in fats by quenching, i.e., scavenging, oxidative free radicals and/or peroxides and hydroperoxides that are formed during fat oxidation, and that are particularly problematic in heated fats.
Thus, in addition to functioning as a plasma cholesterol-lowering neutraceutical ingredient in prepared foods, phytosterols can actually protect fats against oxidation during cooking and storage. These two different and compatible functionalities each support the novel introduction of phytosterols into fat-based compositions or fat-containing prepared foods, e.g., into frying and baking shortenings that are absorbed (e.g., into potato chips) or otherwise incorporated into such prepared foods.
Heat-solubilizing non-esterified phytosterols in fat or oil, followed by cooling and recrystallization, results in formation of triglyceride-recrystallized non-esterified phytosterols (TRPs). The inventors have found that when ingested, regardless of the crystalline size of these fat-recrystallized phytosterols, they were effective at reducing mammalian plasma cholesterol levels. By using cost-effective non-esterified phytosterols, and rendering them bioavailable by thermal recrystallization in fat (i.e., heating and cooling in the frying fat or in the recipe ingredient fat), the invention provides an effective alternative to using more costly forms of phytosterols for lowering plasma and liver cholesterol levels. Such more costly phytosterols include microparticulate powders (ultrafine micron-sized phytosterol powders), chemically modified fat-soluble phytosterols, e.g., fatty acid-esterified phytosterols, emulsified phytosterols, and the more perishable water-oil microparticulate suspensions of phytosterols. Underlying this new method for utilizing phytosterols is the discovery that although a chemically unmodified phytosterol (such as beta-sitosterol) is insoluble in water and poorly soluble in fat, it need not be converted to a microparticulate powder to be effective at reducing plasma cholesterol levels in vivo.
Accordingly, in a first aspect, this invention provides a prepared food product for ingestion by mammals, e.g., by humans. The food product includes an oxidation-resistant fat-based composition substantially free of exogenous solubilizing and dispersing agents for phytosterols. This fat-based composition includes between 75% and 98% by weight of at least one triglyceride-based edible oil or fat, and between 2% and 25% by weight of non-esterified tryglyceride-recrystallized phytosterols (TRPs). At room temperature a limited amount of phytosterol will solubilize, typically such that a fat will include approximately 1.5% by weight of the phytosterols in solution, with any remaining phytosterols remaining insoluble. Thus, if phytosterols are added to the fat to a level from 2% to 25% by weight at room temperature, the fat composition will contain approximately 1.5% solubilized phytosterol and between 0.5% and 23.5% by weight of the phytosterols will remain insoluble at that temperature. Typically the fat-based composition has been partially oxidized by an interval of exposure to air during the manufacture and storage of the prepared food product, and contains a reduced amount of oxidative by-products compared to a similar fat-based composition lacking these non-esterified phytosterols.
Storage stability of the food product may also be referred to as the shelf-life of the product at ambient temperatures. Depending upon the food packaging materials and inert gases utilized in the packaging process, the shelf life for such products may range from approximately one week to a year or more. This fat-based composition has been shown to be cholesterol-reducing as measured in the plasma of mammals, and the TRPs when ingested, are essentially as effective, i.e., as bioavailable, as fat-soluble esterified phytosterols in lowering plasma cholesterol levels. Preferably the shelf-life of a prepared food product containing TRPs is increased at least 5%, 10%, 20%, 30%, 50%, 100%, or even more compared to an otherwise equivalent food product not containing the TRPs.
In particular embodiments, the fat composition includes phytosterols at a level of 2-5%, 5-10%, 10-15%, 15-20%, or 20-25%. In some cases even higher levels maybe added.
In a related aspect, a prepared food product for ingestion by mammals is provided as above except that the fat-based or fat-containing composition has been partially oxidized by an interval of heating, e.g., frying, baking, cooking and the like, in air, and contains a reduced amount of oxidative by-products compared to a similar fat-based composition lacking said non-esterified phytosterols. An upper limit for the interval of heating in air has not been established. However, it is believed that any duration of heating of a conventional fat (one that is free of phytosterols) that results in an acceptable (not excessive accumulation of oxidative by-products, (such as free fatty acids and conjugated dienes), will be satisfactory for the phytosterol-fortified fat. For example, fats and vegetable oils may be exposed to temperatures of approximately 180xc2x0 C. during deep fat frying for periods of time ranging from 5 hr to 25 hr while the prepared food cooked in the oil is exposed to such heat for much shorter intervals, e.g., during cooking (typically several minutes rather than several hours). In any event, a prepared food product as described above may be fried, baked or otherwise heated at least for a time period and to a temperature at least sufficient to dissolve a desired amount (preferably all) of the non-esterified phytosterols added to the fat portion of the fat composition. The fat composition is substantially free of exogenous phytosterol-solubilizing and dispersing agents. Phytosterol enrichment of the fat composition decreases the amount of polar and other oxidative by-products accumulated in the fat and in the prepared food during heating and exposure to air. At least a portion of the non-esterified phytosterols in the fat composition are converted by heating, fully dissolving and subsequent cooling, to triglyceride-recrystallized phytosterols, i.e. TRPs, in which the TRPs contained in the fat composition and in the prepared food product are bioavailable when ingested, to reduce mammalian plasma cholesterol levels.
In certain embodiments, the amount of the edible fat composition in the prepared food product is between 10% and 75% by weight of the food product, e.g., 10-20%, 20-30%, 30-40%, 40-50%, 50-60%, or 60-75%. In other embodiments, the amount of the edible fat composition in the prepared food is lower or higher, e.g., 1-5%, 2-5%, 3-5%, or 4-5%.
In preferred embodiments, the TRPs are formed by heating at least the fat-based composition (or heating. the prepared food product as it contains the fat-based composition) to a temperature of greater than 60xc2x0 C., and fully dissolving the non-esterified phytosterols in the fat composition, and subsequently cooling this composition to room temperature to allow the TRPs to crystallize and be formed.
In another related aspect, a prepared food product for ingestion by mammals is provided that includes a plasma cholesterol-reducing oil or fat composition with improved resistance to oxidation. The oil or fat composition is substantially free of exogenous solubilizing and dispersing agents for phytosterols, and includes between 75% and 95% by weight of at least one triglyceride-based edible oil or fat, and at least 5% by weight of non-esterified triglyceride-recrystallized phytosterols. As described above, typically the phytosterols are soluble in the oil or fat composition at room temperature to a level of approximately 1.5% by weight, so that at least 3% by weight of phytosterols are insoluble at room temperature and have been converted by heating, fully dissolving, and cooling to form triglyceride-recrystallized phytosterols, i.e., TRPs. These TRPs, when ingested, are essentially as effective as fat-soluble esterified phytosterols in lowering plasma cholesterol levels in mammals.
In preferred embodiments, the oil or fat composition includes at least 8%, 10%, 12%, 15%, 17%, or 20% by weight of non-esterified phytosterols or is in a range defined by taking any two of those values as endpoints of the range. As described above, typically the phytosterols are soluble in the fat or oil at room temperature to a level of approximately 1.5% by weight, and the remainder (e.g., at least 6.5%, 8.5%, 10.5%, 12.5%, 15.5%, or 17.5% respectively) is insoluble at room temperature, but is dissolved and tryglyceride-recrystallized by heating to dissolve the phytosterols and cooling. These TRPs, when ingested, are essentially as effective as fat-soluble esterified phytosterols in lowering plasma cholesterol levels in mammals.
In preferred embodiments, the TRPs described above are formed by heating at least the above referenced oil or fat composition (or a prepared food product containing the oil or fat composition, or the oil or fat and the phytosterols as ingredients of the prepared food) to a temperature of greater than 60xc2x0 C., fully dissolving the non-esterified phytosterols in the composition, and subsequently cooling the composition to room temperature to cause the TRPs to be formed.
In certain embodiments, prepared food products are selected from the group consisting of margarine, frying and baking shortenings, mayonnaise, salad dressing, filled dairy products, nut, seed and kernel butters and chocolate (containing cocoa butter). In each of these examples, the phytosterols are dissolved by heating them in the fat portion of these prepared foods, i.e., heating without any aqueous components present. In other embodiments, the prepared food product is a pastry or cake.
In certain embodiments, the prepared food product is fried, baked, or otherwise heat-processed with the oil or fat composition, and/or where the oil or fat composition and phytosterols are added as ingredients in the preparation of the prepared food, wherein such heating allows a portion of non-esterified phytosterols that is insoluble in the oil or fat composition at room temperature to be solubilized and thereby enter and be incorporated into the food product, whereupon during cooling, TRPs are formed in the food product.
In preferred embodiments, the prepared food product is selected from the group consisting of potato chips, French fries, corn chips, tortilla chips, popcorn, and crackers.
Also in preferred embodiments, the food product is cooked, baked, or otherwise heat-processed with the above-described oil or fat composition, allowing a portion of non-esterified phytosterols that is insoluble in the composition at room temperature to be solubilized. During subsequent cooling to room temperature and crystallization of non-esterified phytosterols, a partial or complete solidification of the oil or fat composition can occur. This solidification decreases the oiliness, particularly the surface oiliness, perceived by hand contact with the food product compared to the same food product prepared without non-esterified phytosterols (due to the formation of TRPs in the fat or oil). Solidification or xe2x80x9chardeningxe2x80x9d of oil can also reduce or prevent oil separation in certain prepared foods, and is particularly useful in such foods as peanut butter, soybean butter, sesame seed butter and other seed, bean and nut kernel butters. xe2x80x9cHardeningxe2x80x9d of an edible oil may be compared to that resulting from partial hydrogenation of vegetable oils. Both modifications tend to solidify a vegetable oil by increasing the oil""s melting temperature. However, from a nutritional perspective, addition of phytosterols to ones diet advantageously decreases the level of plasma LDL cholesterol, while addition of partially hydrogenated oils disadvantageously increases the LDL level.
In preferred embodiments, the food product, and more particularly the oil or fat composition within the food product, when heated in air, is more resistant to oxidation and formation of chemically polar degradation products than the same product lacking the non-esterified phytosterols, e.g., as described in Example 3 below.
In preferred embodiments, the food product incorporating the oil or fat composition has a reduced calorie content compared to a similar food product prepared without non-esterified phytosterols, owing to the presence of the non-esterified phytosterols that are calorie-free, and substitute for a portion of triglyceride-based oil or fat normally absorbed or otherwise incorporated into the food product. This statement is explained and supported by Example 4 below.
In preferred embodiments, the non-esterified phytosterols are selected from the group consisting of tall oil-derived phytosterols (such as those obtained from the manufacture of wood pulp from pine trees) and vegetable oil-derived phytosterols (such as those derived from soybean oil).
In another aspect, the invention provides an oxidation-resistant frying or baking shortening that includes: (a) from 75% to 98% by weight of at least one edible triglyceride-based fat or oil; and (b) from 2.0% to 25% by weight TRPs (produced from at least one non-esterified phytosterol compound being solubilized by heating, and allowed to recrystallize in the fat or oil upon cooling). As explained above, typically from 0.5% to 23.5% by weight of phytosterols are recrystallized in the solid phase, and approximately 1.5% by weight of non-esterified phytosterol remains solubilized in the fat at room temperature.
Highly preferably the shortening is substantially free of exogenous solubilizing and dispersing agents for phytosterols, and the rate of formation of polar oxidation products upon heating the shortening to between 160xc2x0 C. and 190xc2x0 C. is reduced, compared to the same shortening lacking the at least one non-esterified phytosterol compound.
Referring to this aspect, the formation of polar oxidation products was determined by measurement of the dielectric constant of the shortening after two hours of heating as described elsewhere herein (see Example 3, second experiment). The term xe2x80x9creduced,xe2x80x9d referring to the rate of formation of polar oxidation products, indicates that the increase in dielectric constant of the shortening is reduced at least 5%, and preferably 7, 8, or 10% or more for the phytosterol-supplemented shortening, compared to the non-supplemented shortening.
In preferred embodiments, the oxidation-resistant frying or baking shortening includes at least one edible triglyceride-based fat or oil selected from the group consisting of natural vegetable oils or fats, natural animal fats and oils, structurally rearranged or modified vegetable and/or animal fats, and combinations thereof.
In preferred embodiments, the oxidation-resistant frying or baking shortening includes at least one non-esterified phytosterol compound selected from the group consisting of vegetable oil-derived phytosterols, tall oil-derived phytosterols, and combinations thereof.
In preferred embodiments, the oxidation-resistant frying or baking shortening includes at least one non-esterified phytosterol selected from the group consisting of beta-sitosterol, beta-sitostanol, campesterol, campestanol, stigmasterol, stigmastanol, brassicasterol, brassicastanol, clionasterol and clionastanol, and combinations thereof.
In another aspect, the invention features a method for reducing plasma cholesterol levels in mammals. The method includes providing a heat-processed prepared food containing an edible fat-based composition that includes between 75% and 98% by weight of at least one triglyceride-based edible fat, and between 2% and 25% by weight of non-esterified triglyceride-recrystallized phytosterols, for ingestion by the mammal(s). Generally, the phytosterol is soluble to a level of approximately 1.5% by weight, such that the insoluble phytosterols in the fat-based composition at room temperature consititute between 0.5% and 23.5%. The fat-based composition is substantially free of exogenous phytosterol-solubilizing and dispersing agents. The insoluble phytosterols have been heat-solubilized and subsequently cooled to form triglyceride-recrystallized phytosterols i.e., TRPs. The TRPs when ingested are essentially as effective as fat-soluble esterified phytosterols in reducing plasma cholesterol levels.
In preferred embodiments, the proportion of non-esterified phytosterols used in the edible fat-based composition for a prepared food is between 3% and 15% by weight of the composition, and more preferably between 5 and 10% of the composition (or other percentage as described for food products herein). Thus, with the latter range, a serving of food containing 10 grams of a fat-based composition, would contain between 0.5 g and 1.0 g of non-esterified phytosterols. This amount is consistent with current recommendations published by the U.S. Food and Drug Administration.
The edible fat-based composition is heated to a temperature of greater than 60xc2x0 C., and preferably between 75xc2x0 C. and 150xc2x0 C., or higher, to dissolve the non-esterified phytosterols in the composition. At a temperature of 60xc2x0 C. or below, the rate of dissolution is slower than desirable, and the concentration of dissolved phytosterols in a fat-based medium is lower than generally desired to be commercially useful or practical.
In preferred embodiments, between 0.5 g and 4.0 g of the non-esterified phytosterols contained in the above prepared food are ingested daily by humans.
In preferred embodiments, the TRPs are formed by heating at least the edible fat-based composition to a temperature exceeding 60xc2x0 C. for a period of time sufficient to dissolve the non-esterified phytosterols in the fat, and subsequently cooling the composition (or the food containing this composition) to room temperature to cause the TRPs to be formed.
In a related aspect, the invention features a method for reducing plasma cholesterol levels in mammals, including providing and regularly ingesting a heat-processed prepared food containing an edible fat-based composition that contains between 75% and 97% by weight of at least one triglyceride-based edible fat, and at least 3% by weight of non-esterified triglyceride-recrystallized phytosterols. Typically the phytosterols are soluble in the fat at a level of approximately 1.5% and the remainder (e.g., 1.5% from a total of 3%) is insoluble at room temperature. The fat-based composition is substantially free of exogenous phytosterol-solubilizing and dispersing agents. The insoluble phytosterols are heat-solubilized and subsequently cooled to form triglyceride-recrystallized phytosterols, i.e., TRPs. The TRPs when ingested are essentially as effective as fat-soluble esterified phytosterols in reducing plasma cholesterol levels.
In certain embodiments, the fat composition contains at least 5%, 7%, 10%, 12%, 15%, 17% or 20% by weight of non-esterified phytosterols (typically the phytosterols are soluble to a level of approximately 1.5% at room temperature and the remainder is insoluble).
In another aspect, a method is provided for preparing a TRP-containing fat-based composition. The method includes (i) providing a triglyceride-based edible fat-containing composition that includes between 2% and 25% by weight of non-esterified phytosterols and not more than 98% by weight of edible fat or oil, in which the composition is substantially free of exogenous phytosterol-solubilizing and dispersing agents, (ii) heating the composition to dissolve (preferably fully dissolve) the non-esterified phytosterols, and, (iii) cooling the composition to room temperature, allowing formation of TRPs. Typically the phytosterols are soluble in the edible fat or oil at room temperature to a level of approximately 1.5%, while the remainder is insoluble at room temperature. In general the fat-containing composition is heated to a temperature of 60-180xc2x0 C., usually 75-150xc2x0 C.
In yet another aspect, a method is provided for preparing a non-esterified phytosterol-fortified prepared food. The method includes: (i) providing an edible fat-based composition that includes between 2% and 25% by weight of non-esterified phytosterols and between 75% and 98% by weight of at least one edible fat or oil, in which the composition is substantially free of exogenous phytosterol-solubilizing and dispersing agents, and one or more other ingredients for the prepared food if any such additional ingredients are used; (ii) cooking or otherwise heating the prepared food ingredients with the composition to allow the non-esterified phytosterols to dissolve in the oil or fat and enter or become integrated into the food product; and (iii) cooling the food product to room temperature to allow formation of TRPs in the composition within the prepared food.
In certain embodiments, the fat-based composition can be used as an ingredient mixed with other ingredients in the preparation of the prepared food, and/or the prepared food product can be cooked in the fat-based composition.
While in most cases the non-esterified phytosterols are recrystallized in the oil or fat prior to combining with other ingredients, for some prepared foods, the phytosterols can be combined with the oil or fat in preparation of the prepared food. Thus, alternatively, the fat or oil and the phytosterols can be added as separate ingredients in such manner that the phytosterols will dissolve in the fat or oil upon heating of the combined ingredients. In some cases, only a portion of the phytosterols added as ingredients will become solubilized, e.g., where only a portion of the phytosterols are in contact with the fat or oil during heating. In cases where the fat-based composition, or the oil or fat and the phytosterols are added as ingredients in preparing the prepared food, typically a number of different ingredients are blended or mixed such that the various ingredients are relatively uniformly distributed throughout the mixture.
The term xe2x80x9cpreparedxe2x80x9d in the context of a xe2x80x9cprepared food productxe2x80x9d refers to a commercially processed and packaged food product containing multiple combined ingredients, in which the processing includes at least one step in which the assembled food product (or one or more triglyceride-based fat or oil ingredients that are either contacting, or being combined into the food product), are heated together with a suitable quantity of phytosterol ingredient(s), to a temperature sufficient to dissolve the phytosterols in the fat or oil, and often substantially higher than this temperature, and for a period of time sufficient to process, cook, fry or otherwise complete the heat-preparation of the food product. Upon cooling, a portion of the phytosterols recrystallize in a fat or oil component of the processed prepared food product. Examples of such prepared food products include potato chips (containing at least potatoes, frying fat or oil, and phytosterols), French fries, corn chips, tortilla chips, popcorn, crackers, peanut butter, soybean butter, sesame seed butter and other nut kernel butters, mayonnaise, processed cheese, chocolate and the like.
The term xe2x80x9cfatxe2x80x9d may be used broadly and generally, referring to an edible triglyceride that may be either liquid (also specifically termed oil) or solid at room temperature (also specifically termed fat), and that is derived from a single vegetable source (e.g., soybean, cottonseed, corn) or an animal source (beef tallow, pork lard) or a blended combination of sources. Unless specifically limited to edible triglyceride compositions that are solid at room temperature, use of the term xe2x80x9cfatxe2x80x9d includes oils. Also unless clearly indicated to the contrary, the term xe2x80x9cfatxe2x80x9d also includes chemically and enzymatically modified triglyceride-based liquid and solid fats and blends thereof (e.g., hydrogenated, partially hydrogenated, chemically or enzymatically interesterified, or assembled, i.e., xe2x80x9cstructuredxe2x80x9d triglycerides and combinations thereof.
The phrase xe2x80x9cimproved resistance to oxidationxe2x80x9d for a fat that contains non-esterified phytosterols refers to a fat exhibiting at least a 10% reduced rate of degradation by oxidation in air, compared to oxidation of the same fat without phytosterols. This differential oxidation rate is particularly evident during heating of the oil, e.g., frying with the oil at a temperature of 160-190xc2x0 C. Oxidation rate is evidenced by one or more physical measurements such as dielectric constant measurement of polar oxidation products formed in the fat, AOM (accelerated oxidation measurement, OSI (oxidative stability index), or organoleptic quality (tasting f or rancidity). The extent of oxidative protection provided by non-esterified phytosterols dissolved in fat heated to 180xc2x0 C. is a function of the type of fat and the concentration of phytosterols in the fat. Improved resistance to oxidation is particularly evident in a vegetable oil containing polyunsaturated fatty acids, e.g., soybean, corn and canola oil. When 10% by weight soybean-derived phytosterols is dissolved in such oils, the rate of oxidation, i.e., formation of polar oxidation products, in the heated oils is at least 10% lower than the rate in the same oil lacking phytosterols. Preferably, the rate of oxidation is at least 20% lower, and more preferably, the rate is 30%, 40% or even 50% lower than the rate in the same oil lacking phytosterols.
The term xe2x80x9cpartially oxidizedxe2x80x9d refers to a fat-based composition that has been exposed to air either with or without heating, e.g., frying or baking and that has at least begun to accumulate oxidative by-products whose concentrations are measurable either in the oil or in the vapor above the oil by conventional means, e.g., by conductivity, dielectric constant, and free fatty acid content.
It is believed that oxidative protection of fats and oils provided by phytosterols has not been reported previously. Also, phytosterols are not recognized as antioxidants or as scavengers or quenchers of free-radicals or peroxides and hydroperoxides formed during oxidation of polyunsaturated fatty acid moieties. In searching for a rational explanation for this oxidative protection, Applicants have looked to literature describing various properties of cholesterol. Of course xe2x80x9ccholesterol fortificationxe2x80x9d of a food product would be nutritionally undesirable and, indeed, phytosterol fortification is intended to reduce cholesterol uptake. However, the cholesterol molecule is structurally related to the phytosterols, i.e., addition of an ethyl side group to beta-sitosterol generates cholesterol. U.S. Pat. No. 6,214,534 by Horowitz et al. describes several UV light photodynamic quenchers including vitamins, thiols, cholesterol, and several other compounds that react with, and inactivate both free radicals and reactive forms of oxygen. Since free radicals, peroxides and hydroperoxides are produced during the oxidation of polyunsaturated fatty acid groups in triglycerides, phytosterols dissolved in fat may inactivate these reactive compounds, as with cholesterol described in the photodynamic system of Horowitz et al. While the phytosterols may act in this manner, the present invention is not limited by this explanation.
The term xe2x80x9cediblexe2x80x9d in the context of an oil or fat-based composition means that the composition is suitable for use in mammalian, e.g., human, foods, dietary supplements and pharmaceutical preparations.
The term xe2x80x9cexogenous phytosterol-solubilizing and dispersing agentsxe2x80x9d refers to agents other than triglycerides in the prior art, that have been added to triglyceride-based oils and fats to promote the cholesterol-lowering efficacy of phytosterols (see discussion above in the Background section). A partial list of these agents includes monoglycerides, diglycerides, lecithin, vitamin E, the sorbitans and other surfactants, and fatty acids chemically esterified with phytosterols.
The term xe2x80x9csubstantially free,xe2x80x9d referring to any presence of exogenous solubilizing and dispersing agents for phytosterols, means that either zero percent, or in any event, less than 50% (and preferably less than 25%) of the amount of such an agent or agents that would be required in the absence of triglycerides, to achieve solubilization or dispersal of non-esterified phytosterols (at room temperature) that have been added to the referenced composition. Provided that the phytosterols are recrystallized in triglycerides, triglycerides alone are sufficient for phytosterol bioavailability, i.e., effectiveness in plasma cholesterol reduction. Therefore, any addition of such a non-triglyceride solubilizing or dispersing agent to a fat-based composition containing TRPs is considered gratuitous and optional.
The term xe2x80x9cphytosterolxe2x80x9d refers to any of a group of sterols derived from plants (see examples below in Example 1).
The term xe2x80x9cnon-esterified phytosterolsxe2x80x9d refers to forms of phytosterols that are free of ester chemical side chains. Conversely, esterified phytosterols are most commonly fatty acid-esterified phytosterols manufactured to promote phytosterol solubility in fat. Non-esterified phytosterols are defined herein to include both the non-esterified sterol and stanol forms of phytosterols (see Example 1 below). According to the present invention, phytosterols are dissolved in oil or fat before recrystallization, and therefore the particle size, texture, etc. of the material can be coarse for reasons of economy, i.e., chemical dissolution reduces the material to molecular dimensions. Dissolution of more costly forms of phytosterols, e.g., ultrafine micron-sized phytosterol powders, would be economically wasteful, but can also be done.
The composition which includes between 75% and 98% by weight of at least one triglyceride-based edible oil or fat, allows between 2% and 25% by weight of non-esterified phytosterols to be added to the same composition. A 3% to 10% by weight concentration range is a preferred range. Accordingly, at the 3% level, a food that contains 10 g of fat per serving will provide at least 0.3 g of phytosterols per serving. In the case of pharmaceutical preparations, the composition may include as little as 50% by weight of at least one triglyceride-based edible oil or fat, to allow between 3% and 50% by weight of non-esterified phytosterols to be added to the same composition.
The process of treating the non-esterified phytosterols by xe2x80x9cheating, fully dissolving, and coolingxe2x80x9d refers to a process that: (i) heats the phytosterols together with triglyceride-based fat or oil (and optionally other food ingredients constituting a prepared food product) to a temperature of greater than 60xc2x0 C. until the phytosterols have dissolved, and then (ii) cooling the heated product and allowing the triglycerides to associate with the recrystallizing phytosterols. Flash-chilling with chilled air or with a chilled water jacket may tend to precipitate and segregate the phytosterols from the triglycerides, preventing optimal recrystallization. Conventional or normal ambient air cooling rates of prepared foods containing heated triglycerides and phytosterols is preferable to flash cooling. For example, in may cases cooling of a fat-based composition or prepared food to room temperature will occur over a period of 5 minutes to 2 hrs, although longer or shorter times can be used.
The term xe2x80x9ctriglyceride-recrystallized phytosterolsxe2x80x9d or TRPs and the process of heating and cooling these ingredients is described elsewhere herein. The term xe2x80x9crecrystallizedxe2x80x9d is distinguished from the term xe2x80x9csolubilizedxe2x80x9d (in which the phytosterols are dissolved to form a clear solution). Recrystallized is meant to indicate that the phytosterols after initially being dissolved in one or more triglyceride-based fats or oils, are allowed to cool and recrystallize in the oil or fat. By physical analyses (light microscopy of lipid stained crystals, and melting temperature determinations described elsewhere herein), Applicants have determined that such recrystallization results in fats and/or oils, i.e., triglycerides, becoming intimately associated with crystallizing phytosterols. The resulting products are mixed and/or interrupted crystal structures having melting temperatures reduced below that of the phytosterols alone. It is believed that these physically destabilized, triglyceride-containing crystals are more easily emulsified and/or dissolved in the mammalian gut, resulting in improved phytosterol bioavailability and therefore more effective plasma cholesterol reduction in vivo. As noted above, a proportion of the phytosterols is soluble in the fat at room temperature (typically at a concentration of about 1.5%). Therefore, when a combination of phytosterols and fat is heated to dissolve solidified (crystallized) phystosterols and then cooled, phytosterols that cannot remain in solution at room temperature solidify or recrystallize, but a portion remains dissolved in the fat. Thus, unless clearly indicated to the contrary, reference herein to xe2x80x9ctriglyceride-recrystallized phytosterolsxe2x80x9d or xe2x80x9cTRPsxe2x80x9d includes both the dissolved phytosterols as well as the re-solidified or recrystallized phytosterols.
The term xe2x80x9ceffectivexe2x80x9d refers to the extent to which plasma cholesterol levels in mammals are reduced by regular, e.g., daily, twice daily, or thrice daily ingestion of the recommended 1-2 gram dose (or the appropriate divided dose) of phytosterols. In a random population of human adults, a 5% to 15% or greater lowering of total cholesterol in the plasma caused by ingestion of phytosterols is considered effective.
The term xe2x80x9cesterified phytosterolsxe2x80x9d refers to phytosterols (plant sterols and stanols) that have been joined through an ester linkage to fatty acids using a chemical, enzymatic, combination, or other process. The commercial margarines Benecol(copyright) and Take Control(copyright) discussed above, incorporate such esterified phytosterols. Therefore, xe2x80x9cnon-esterified phytosterolsxe2x80x9d refers to phytosterols that have not been esterified to fatty acids as described.
The term xe2x80x9creduced surface oilinessxe2x80x9d means that upon routine handling of the prepared food, less oil is transferred from the food to ones hands (or to an absorbant surface) than would otherwise occur if the food were prepared with the oil or fat alone (see Example 5 below).
For the definition of any other fat and oil-related terms that have not been defined herein, the reader is referred to the reference book, Bailey""s Industrial Oil and Fat Products, Fourth Edition, Daniel Swem, editor, John Wiley and Sons, N.Y., 1979.
By xe2x80x9ccomprisingxe2x80x9d is meant including, but not limited to, whatever follows the word xe2x80x9ccomprisingxe2x80x9d. Thus, use of the term xe2x80x9ccomprisingxe2x80x9d indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present. By xe2x80x9cconsisting ofxe2x80x9d is meant including, and limited to, whatever follows the phrase xe2x80x9cconsisting ofxe2x80x9d. Thus, the phrase xe2x80x9cconsisting ofxe2x80x9d indicates that the listed elements are required or mandatory, and that no other elements may be present. By xe2x80x9cconsisting essentially ofxe2x80x9d is meant including any elements listed after the phrase, and limited to other elements that do not interfere with or contribute to the activity or action specified in the disclosure for the listed elements. Thus, the phrase xe2x80x9cconsisting essentially ofxe2x80x9d indicates that the listed elements are required or mandatory, but that other elements are optional and may or may not be present depending upon whether or not they affect the activity or action of the listed elements.
Additional aspects and embodiments will be apparent from the following Detailed Description and from the claims.
Recently, a number of investigators have described a variety of methods for producing very small particles or microcrystals of phytosterols. It is believed that such small particles have greater efficacy in being dispersed in the GI tract and controlling plasma cholesterol levels. U.S. Pat. No. 6,129,944 by Tiainen et al. describes the production of a microcrystalline phytosterol product useful as a cholesterol-lowering agent, formed by pulverizing, i.e., dry or wet grinding, a crystalline phytosterol to produce microparticles having a preferred mean particle size of approximately 5-10 microns. The microcrystalline phytosterol product can be mixed with a sweetening agent and water or alternatively, mixed with another carrier such as fat to form a microparticulate emulsion. There is no suggestion by Tiainen et al. or any other investigator of which the inventors are aware that microcrystalline phytosterols after being formed, should be heated or dissolved in such a fat or oil. Such heating in oil, as described for the present invention, would be expected to destroy the sized microparticles described by Tiainen et al.
As described herein, phytosterols are recrystallized with triglycerides (e.g., vegetable oil, shortening, or the like). The first step involves heating the triglyceride(s) and phytosterol(s) until the phytosterols are dissolved. This phytosterol-triglyceride solution is used to contact, or be combined with the food product being fried, cooked or otherwise heated. (Alternatively, the fats and the phytosterols are added as separate ingredients in the preparation of a prepared food.) Subsequently, the prepared food product is cooled (preferably by contacting the heated food product with ambient air). Under the light microscope (600xc3x97 magnification), it is seen that phytosterols that have been recrystallized in vegetable oil, e.g., soybean oil, tend to form a diversity of macrocrystalline structures spanning tens or hundreds of microns. This material when tasted, has a surprisingly soft and agreeable mouth feel, and includes elongated hexagonal crystals, radially extending branched crystalline needle structures (appearing as wispy ball-shaped structures), and large extended flat plate crystals. On the other hand, phytosterols that are recrystallized by quick-chilling to room temperature (e.g., by ice chilling to room temperature in a few seconds rather than by ambient air contact), tend to form harder, smaller, more homogeneous needle-like micro-crystals having diameters of only a few microns, i.e., 1-4 microns.
The temperature required to re-dissolve the above crystals in the surrounding vegetable oil differs significantly depending upon the rapidity of recrystallization. For example, 10% by weight soybean-derived phytosterols that were recrystallized at room temperature in soybean oil, redissolved in the oil at a temperature of 65xc2x0 C. On the other hand, the more rapidly ice-recrystallized phytosterols described above required a higher temperature (72xc2x0 C.) to be redissolved. By comparison, the same amount of phytosterol (as a dry powder) initially placed in soybean oil, required a temperature of nearly 85xc2x0 C. to be dissolved. The observations on recrystallization (coupled with the microscopic analysis of crystalline sizes and shapes) suggested that slower recrystallization allows formation of mixed composition triglyceride-containing (larger) phytosterol crystals. These crystals would be expected to redissolve more easily, i.e., at a lower temperature, than the rapidly formed crystals.
To determine whether the larger crystals contained any triglycerides, these crystals were washed and centrifuged twice in ethanol. Next, the crystals were stained with a saturated Sudan Black solution (60% by weight ethanol in water) to visualize any lipids. Light microscopy confirmed that the lower melting point larger crystals (but not the higher melting point small needle-shaped crystals) contained multiple internal layers and occlusions of lipid. It is reasonable to conclude that the intimate association of triglycerides and phytosterols that results from fully dissolving and then recrystallizing phytosterols in fats, yields crystals having a reduced melting temperature. These crystals appear to provide dietary phytosterols in a highly bioavailable form useful for reducing plasma cholesterol levels.
While it has been recently reported that a crystalline complex can be formed by combining phytosterols and monoglyceride emulsifiers (see above, U.S. Pat. No. 6,267,963), the existence and utility of triglyceride-recrystallized phytosterols have not been previously described. In fact, Applicants have not found any prior reference to formation of a mixed crystalline complex or association between triglycerides and phytosterols that enhances phytosterol bioavailability.
Non-esterified phytosterols are known to have a very limited solubility (to a concentration of approximately 1.5% by weight) in an edible oil or fat at room temperature. Nevertheless, between 2% and 25% by weight of non-esterified phytosterols (e.g., semi-pure or purified phytosterols from soybeans or pine tree tall oils), can be readily and conveniently dissolved in edible oil or fat by heating to a temperature of 60xc2x0 C. or greater, and preferably 75xc2x0 C.-100xc2x0 C. or above (the required temperature depending upon the concentration of phytosterols to be dissolved). Subsequently, as the heated composition is cooled to room temperature, a substantial portion of the solubilized phytosterol precipitates, i.e., is recrystallized, in the triglyceride-based oil or fat in the form of a Triglyceride-Recrystallized Phytosterol composition or complex (hereinafter abbreviated xe2x80x9cTRPxe2x80x9d, xe2x80x9cTRP composition or TRP complexxe2x80x9d).
Remarkably, the TRP composition formed in this manner has been found to be as potent in the mammalian diet at reducing the levels of plasma and liver cholesterol as fatty acid-esterified phytosterols that are fully soluble at room temperature. In the first direct comparison between non-esterified phytosterols and equivalent amounts of phytosterols as sterol esters in the same experiment, it was found that non-esterified phytosterols fully dissolved in oil by heating ( greater than 60 degrees C., and preferably  greater than 80 degrees C.), and provided equivalent (or even greater) reductions in plasma and liver cholesterol as compared to equivalent amounts of esterified sterols. In the context of cholesterol reduction, the term xe2x80x9cgreaterxe2x80x9d means that the cholesterol reductions measured and reported herein and in the Hayes reference are greater than those reported by Ntanios and Jones (Biochim. Biophys. Acta (1998) 1390:237-244) for the same levels of sterols, in which the sterols were incompletely dissolved in fat. While TRPs may have been accidentally produced in the past in the course of heating and cooling non-esterified phytosterols and fats, their utility for plasma cholesterol reduction would not have been recognized due to their poor room temperture solubility.
The presently described TRP composition is more convenient and cost-effective than esterified phytosterols or phytosterol-containing compositions that have been supplemented with solubilizers, emulsifiers, antioxidants and other additives for inclusion in foods. The TRP composition also has a significant advantage over the finely milled and microcrystalline powdered forms of phytosterols described by Tiainen et al. and Jones et al., in light of the considerable cost associated with producing these micron-sized powders. The present composition is particularly useful in preparing fat-based foods such as shortening, margarine, mayonnaise, salad dressing, peanut butter and the like, and processed food products including fried and baked snack foods.
Surprisingly, as illustrated below, the presence of dissolved phytosterols in a heated oil or fat, improves the triglyceride""s oxidative stability, and at ambient temperature, decreases the surface oiliness of foods fried in the triglyceride-based composition. At the same time, the caloric fat content of a food prepared in or with the TRP-containing composition is reduced. While other investigators have found that finely milled or microcrystalline preparations of non-esterified phytosterols that have not been initially heat-solubilized in an oil or fat, can also function efficiently to reduce mammalian plasma cholesterol levels, the additional benefits described above are obtained only after heat-solubilization. For example, heat-solubilization in a triglyceride-based edible oil allows non-esterified phytosterols to freely enter a food product as it is being fried in the oil, whereas particles of phytosterols would be excluded. Likewise, suspended particles would not be expected to improve the oxidative stability of an oil.
For the purpose of this invention, the fat or oil used as a vehicle or carrier for the phytosterol herein, is a conventional triglyceride-based cooking fat or oil that is substantially free of phytosterol solubilizing agents, dispersants and/or detergents (collectively termed xe2x80x9coil emulsifiers or additivesxe2x80x9d). Examples of such fats and oils include natural vegetable oils, interesterified fats and oils, and partially hydrogenated vegetable oils, animal fats and combinations thereof.
Unlike recently described compositions for oils and fats containing phytosterols described above in the Background, the presently described triglyceride-based composition contains substantial amounts of insoluble phytosterol (recrystallized in fat) rather than solubilized phytosterol, and is substantially free of the above-described oil additives for dispersing or solubilizing phytosterols. The composition is particularly useful in preparing fat-containing foods that do not require oil transparency at ambient temperatures. This is true of margarines, shortenings, mayonnaise, cheese and other dairy fat-containing products, some salad dressings, and many other foods including processed foods that are fried, baked or otherwise prepared by cooking or heating in, or in combination with fat or oil. Examples of such foods include the snack food category, e.g., potato chips, crackers, and the bakery category, e.g., donuts, pies, cakes, and the like.
The present invention describes compositions and methods for introducing substantially fat-insoluble non-esterified phytosterols into foods, including snack foods, by means of the standard fat or oil that is used in the frying or baking of such foods. It was the inventors"" intention to compare the efficacy of using non-esterified phytosterol preparations recrystallized in edible fat and used in foods, e.g., fried foods, with that of more costly diglyceride-solubilized or fatty acid esterified phytosterols in limiting cholesterol absorption in the gut, and lowering plasma cholesterol levels. Surprisingly, the phytosterols recrystallized in fat that has been incorporated into such foods are very effective, i.e., bioavailable, in reducing plasma and liver cholesterol levels. It is believed that this cholesterol-lowering efficacy compares favorably with that of fully solubilized phytosterol preparations (e.g., phytosterols esterified with fatty acids to assure solubility in fat-containing products such as Benecol(copyright) and Take Control(copyright) margarines).
As an unanticipated benefit and utility in the present invention, the presence of 5-10% or more by weight of phytosterol that has been recrystallized with triglycerides in the oil portion of fried snack food (e.g., potato chips) has been found to decrease the surface oiliness of fried food when compared to food fried in oil lacking the phytosterol. Applicants have also found that the presence of either soybean oil-derived phytosterols or tall oil-derived phytosterols in vegetable oil during frying, helps in chemically stabilizing the oil against oxidation by reducing the rate of appearance and the amount of polar breakdown products in the oil. To the extent that the phytosterols replace a portion of the oil in such a blend, the phytosterols also serve to reduce the caloric fat content of a food cooked in the blend. Thus, the present invention also provides methods for decreasing the surface oiliness of fried foods, and the resulting fried foods, and methods for providing reduced calorie food, utilizing TRPs as described herein.
Except for micron-sized finely milled powders of non-esterified phytosterols described by Tiainen et al. and Jones et al. (see above), as well as previously described emulsified preparations, the non-esterified phytosterols have been thought to lack xe2x80x9cbioavailabilityxe2x80x9d relative to esterified sterols and stanols, as emphasized in the introductory references. In this instance, bioavailability for a given quantity of phytosterol means the potency of that particular physical and/or chemical form of phytosterol in lowering the plasma level of total and LDL cholesterol. Despite the limited solubility of non-esterified phytosterols in fats and oils at room temperature, it has been discovered that concentrations of between 2% and 25% by weight non-esterified phytosterols (e.g., soybean oil-derived mixed prilled sterols or stanols or tall oil-derived sterols and stanols) can be conveniently and rapidly dissolved by mixing or other agitation in diverse oils, fats and fat-containing foods, e.g., cooking or salad oil, shortening, peanut butter and dairy cream, heated to a temperature of greater than 60xc2x0 C., and preferably between 75xc2x0 C. and 150xc2x0 C., or above. At higher temperatures such as 180xc2x0 C., a heated oil or fat, e.g., corn, canola, cottonseed, soybean oil, or palm oil that contains heat-solubilized phytosterols is useful in the preparation (e.g., frying and baking) of potato chips and other snack foods. When such heat-solubilized phytosterols are cooled and recrystallized in such fats or fat-containing foods, their ability to lower plasma cholesterol levels is excellent (see nutritional studies below).
The fat compositions and food products of the present invention can be prepared by conventional methods, with the addition of phytosterols (e.g., as described herein). Persons familiar with preparation of fat compositions and food products can routinely select suitable components for a particular product.
Preliminary Study. Reducing Plasma Cholesterol Using Non-Esterified Phytosterols and an Emulsifier in Dietary Fat.
The efficacy of adding 0.25% by weight soybean oil-derived prilled sterols and 0.25% soybean prilled stanols to a hamster diet containing 0.05% cholesterol to reduce the animal""s plasma cholesterol level was investigated. Hamsters were fed a cholesterol-containing diet in which the dietary fat (30% soybean oil, 50% palm oil and 20% canola oil-providing approximately equal amounts of saturated, monounsaturated and polyunsaturated fatty acids) was either supplemented or unsupplemented with up to 6% by weight of an emulsifying agent (subsequently reported by Goto et al. in U.S. Pat. No. 6,139,897) to enhance the solubilization of sterols and stanols in the fat portion of the diet. It was expected that this agent, a mono- and diglyceride emulsifier (40% glyceryl monocleate+60% glyceryl dioleate), which readily dissolves both sterols and stanols, would enhance the ability of these phytosterols to lower hamster plasma cholesterol levels.
Surprisingly, each cholesterol-lowering regimen (i.e., sterols and stanols, each tested separately after heating with dietary fat; or stanols combined with either 3% or 6% by weight of the above emulsifier in the heated dietary fat) was found to reduce the plasma cholesterol level to the same extent. More specifically, while the plasma total cholesterol value (TC) in hamsters fed a cholesterol-supplemented diet was found to average 185 mg/dL, and the TC value in hamsters fed a cholesterol-free diet averaged 135 mg/dL, all of the dietary regimens incorporating a low level (0.25% by weight) of phytosterols (5:1 sterol-to-cholesterol) resulted in significantly reduced TC values averaging 160xc2x115 mg/dL. ( Liver EC, i.e., esterified cholesterol, showed that 1:3 monoglycerides improved efficacy, as well) These results suggested that phytosterols can function effectively to lower TC both when they are solublized in the diet (e.g., using mono- and diglycerides added to a dietary fat) and when they are recrystallized in the triglyceride (fat) portion of the diet, after being initially solubilized in the heated fat. It is also possible that finely milled micron-sized powder phytosterol preparations would function well to lower TC (without fat recrystallization), but these preparations have the disadvantage of greater manufacturing cost.